Power Management

Some components in a computer system do not need to run continuously. The purpose of power management is to conserve battery life by shutting down these components when they're not needed.

Most portable computers include power-saver modes that suspend system operations when the computers are not in use. Different manufacturers have different names for their power-saver modes such as suspend, hibernate, or conserve, but they all usually refer to two different states of power conservation: One state continues to power the system's RAM, and the other does not.

Generally, the suspend mode virtually shuts down the entire system after a certain period of inactivity. However, power continues to be supplied to RAM, and the system can be reawakened almost immediately.

The hibernate mode writes the entire contents of memory into a special swap file and then shuts down the system. When reactivated, the file is read back to memory. The hibernate mode takes a little longer to reactivate than the suspend mode, but it conserves more battery life. In some systems, the swap file used for the hibernate mode is located in a special partition of the hard drive. If it is inadvertently destroyed, it might require a special utility from the manufacturer to re-create it.

A document jointly developed by Intel and Microsoft, the Advanced Power Management (APM) standard, has been, for the most part, responsible for defining the interface (interaction) between the power-management policy driver and the operating system. This interface is usually implemented in the system BIOS.

Another standard currently under development by Intel, Microsoft, and Toshiba is called the Advanced Configuration and Power Interface (ACPI). This standard is designed to place the power-management functions under the control of the operating system. As power-management techniques develop, it becomes difficult for the BIOS to maintain the complex information states needed to run the more advanced functions. Placing power management under the control of the operating system allows applications to interact with the operating system to let it know which of its activities are crucial and which can wait until the next time the hard disk drive is activated.

New Technology

Battery technology has trailed behind nearly all the other advances of the portable system. A battery life of two hours is considered very good even when a system's power-saving features are utilized. Some manufacturers are designing systems that hold two batteries to try to overcome this limitation.
A fourth type of battery technology—the lithium polymer—has been in development for several years, but it has not yet appeared on the market. Lithium polymer batteries can be formed into thin, flat sheets and installed behind the LCD panel. They provide approximately 40 percent more battery life while adding far less weight to the system.

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All battery types function best if they are completely discharged before recharging. Even lithium ion batteries perform better and last longer if they are discharged before being recharged. You can also store charged batteries in the refrigerator to help them maintain their charges longer.

Proper Battery Disposal
Many people give no thought to discarding exhausted batteries in the nearest trash container, but you should take a more professional approach. Batteries contain hazardous and environmentally detrimental materials. Be sure and check your company policy and recommendations from the manufacturer before disposing of any battery. Failure to do so is both poor practice and an invitation for a fine.

Batteries

A great deal of technology has been developed to extend battery life and improve power management in portable systems. However, battery life is still one of the most significant complaints about portable systems. Even though power management and batteries themselves have improved dramatically over the last few years, the power needed to run faster processors and external devices has increased, leaving battery life about the same. Actual battery life depends as much on how the computer is used as it does on power-management technology. Simply put, the more you ask the computer to do, the shorter the battery life. Today, battery life is still an issue with portable system users. Most systems use one of three types of batteries.

Nickel Cadmium Batteries

The oldest of the three technologies, nickel cadmium (NiCad) batteries are rarely used today. They have a short life and are sensitive to improper charging and discharging. After being charged, NiCad batteries hold a charge very well. How-ever, their life can be severely shortened if they are not fully discharged before recharging or if they are overcharged.

Nickel Metal Hydride Batteries

Nickel metal hydride (NiMH) batteries have a longer life than NiCad batteries (about 50 percent longer) and are less sensitive to improper charging and discharging. They are also more expensive than NiCad batteries and don't hold a charge as well when not used. They usually cannot be recharged as many times. They are, however, used in most portable systems, especially those at the lower end of the market.

Lithium Ion Batteries

Lithium ion batteries cannot be overcharged, hold a charge well when not in use, and last longer than the other two types of batteries. They are also proficient at handling the heavy-duty power requirements of today's higher-end portables. Because they are the most expensive of the three battery technologies, lithium ion batteries are usually found only in high-end systems. Unfortunately, these batteries can be used only in systems specifically designed for them.

CAUTION

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Never install a lithium ion battery in a system designed for a NiCad or NiMH battery. Doing so could result in a fire.

Buying a system with a lithium ion battery does not necessarily ensure a longer battery life. Some manufacturers take the opportunity to make the battery smaller because it is more powerful, thereby saving some space inside the computer while delivering the same performance as a NiCad or NiMH battery.

USB Ports

The addition of USB (universal serial bus) technology to portables has made it much easier to add new devices or share them with other computers, like the owner's desktop machine. The hot-swap capability, coupled with the wide range of products (from printers and scanners to Zip drives and modems), makes this a must-have for any new portable. Keep in mind that there are PCMCIA USB cards on the market that can add the functionality to older machines as well.

Pointing Devices

Today's portable computers come with built-in pointing devices. Most of these pointing devices are one of three types: trackball, trackpoint, or trackpad.

• Trackball. This small ball (approximately .5 inch in diameter) is partially embedded in the keyboard below the spacebar. The user's fingers manipulate the ball. These devices are accurate and serviceable, but they are unpopular because of their tendency to gather dirt and dust, which dramatically reduces performance.

• Trackpoint. IBM developed the trackpoint, which many manufacturers install in their systems. It is a small, rubberized button (approximately .25 inch in diameter) located above B and below G and H on the keyboard. The user nudges it in any direction (rather like a tiny version of a joystick) to move the cursor around the screen. It is convenient because the user's hands don't need to leave the keyboard to manipulate the trackpoint.

• Trackpad. The trackpad (also known as the touchpad) is the most recent development of the three. It is an electromagnetically sensitive pad measuring about 1 inch × 2 inches located in the keyboard below the spacebar. It responds to the movement of a finger across its surface to move the cursor. Tapping the pad simulates mouse clicks (although buttons are also provided). It is a truly innovative device, but does tend to be overly sensitive to accidental touches and taps. It is also sensitive to humidity, so moist fingers can cause unpredictable performance.

Keyboards

Portable keyboards are integrated into the one-piece unit and are therefore very difficult to repair or replace. Unfortunately, the keypad is almost always the first component to fail in a portable. The functionality and durability of the keyboard should be an important concern when purchasing a portable system.

Today's portable keyboards are approaching the size and functionality of desktop systems, thanks to the larger screens found on most systems. This has created more space for manufacturers to utilize in the overall design.

Removable Media

Portable systems are now equipped with other types of storage media that can provide access to large amounts of data. CD-ROM and Zip drives are now available, as well as standard floppy disk drives. Just as in desktop counterparts, CD-ROM is becoming standard on portables.

The swappable drive bay is increasing in popularity. This product allows the user to switch one of several types of components in the unit. For example, you might not need a floppy disk drive when traveling, so you can insert an extra battery.